The reason for investor optimism can be summed up in two words: Marissa Mayer.

Yahoo’s new CEO has charmed investors with her plans to bring the floundering search engine into the future. Despite her warnings that change won’t happen over night, Mayer, of Google fame, seems to have won Wall Street’s confidence.

Mayer is focusing on devising a comprehensive mobile strategy for the search engine. Mayer, who revealed her plan in a conference call with analysts Oct. 22, said although Yahoo has under-invested in mobile in the past, it is “a huge wave for us to ride.”

She is also determined to work her magic on Yahoo by focusing on users’ “daily habits” such as e-mail, the home page and Internet search as well as mobile devices.

Mayer has also discussed forming a closer relationship with Microsoft, its software provider and Web search partner, while using technology to bolster its display ads business through such features as automated buying.

The 37-year-old, who took on the CEO position in July has already made her presence known with a thorough redesign of Yahoo.com.

Until the redesign, which was officially unveiled last month, the search engine website had sported the same look for years.

Investors and analysts, meanwhile, are rejecting rumors that Yahoo and Facebook will join forces to offer search solutions.

Facebook, however, issued a statement to the media Nov. 19 denying any such claims.

“People expect a better search experience on Facebook,” a company statement reads. “We are working on improvements to better meet those expectations but are not in talks to enter into a new search partnership.”